[U-Boot] [PATCH] serial: 16550: Add JZ47xx support

[Simon Glass]

Hi Marek,

On 26 May 2016 at 10:34, Marek Vasut <marex at denx.de> wrote:
> On 05/26/2016 03:29 PM, Simon Glass wrote:
>> Hi Marek,
>>
>> On 25 May 2016 at 16:35, Marek Vasut <marex at denx.de> wrote:
>>> On 05/26/2016 12:31 AM, Daniel Schwierzeck wrote:
>>>>
>>>>
>>>> Am 26.05.2016 um 00:21 schrieb Marek Vasut:
>>>>> On 05/26/2016 12:17 AM, Daniel Schwierzeck wrote:
>>>>>>
>>>>>>
>>>>>> Am 25.05.2016 um 02:19 schrieb Marek Vasut:
>>>>>>> The Ingenic JZ47xx requires special bit (UART_EN) set in FCR register
>>>>>>> in order to work at all. Add this special case handling into the driver.
>>>>>>>
>>>>>>> Signed-off-by: Marek Vasut <marex at denx.de>
>>>>>>> Cc: Tom Rini <trini at konsulko.com>
>>>>>>> Cc: Simon Glass <sjg at chromium.org>
>>>>>>> Cc: Daniel Schwierzeck <daniel.schwierzeck at gmail.com>
>>>>>>> Cc: Paul Burton <paul.burton at imgtec.com>
>>>>>>> ---
>>>>>>>  drivers/serial/ns16550.c | 8 ++++++++
>>>>>>>  1 file changed, 8 insertions(+)
>>>>>>>
>>>>>>> diff --git a/drivers/serial/ns16550.c b/drivers/serial/ns16550.c
>>>>>>> index 30ba0aa..1323881 100644
>>>>>>> --- a/drivers/serial/ns16550.c
>>>>>>> +++ b/drivers/serial/ns16550.c
>>>>>>> @@ -50,6 +50,14 @@ DECLARE_GLOBAL_DATA_PTR;
>>>>>>>  #endif
>>>>>>>  #endif
>>>>>>>
>>>>>>> +#ifdef CONFIG_ARCH_JZ47XX
>>>>>>> +#undef UART_FCRVAL
>>>>>>> +/* Ingenic JZ47xx SoCs require that a 'UART Module Enable' bit be set */
>>>>>>> +#define UART_FCR_UME              0x10
>>>>>>> +#define UART_FCRVAL (UART_FCR_FIFO_EN | UART_FCR_RXSR |   \
>>>>>>> +               UART_FCR_TXSR | UART_FCR_UME)
>>>>>>> +#endif
>>>>>>
>>>>>> I think this could be added as DT property
>>>>>
>>>>> Not for SPL, which has 14 kiB size limit and it is itching to overflow.
>>>>> I am literally counting bytes in the SPL and removing slop from
>>>>> structures to make it fit, just barely. With the USB loader, I can
>>>>> brutalize the SPL into having extremely rudimentary UART support now
>>>>> (like printch() being the most advanced output mechanism, but you can
>>>>> only use it three times, otherwise the code won't fit and the board is
>>>>> eaten by demons) and this is where this patch comes into play.
>>>>>
>>>>> So yes, for full u-boot, this _should_ be part of DT. For SPL, please apply.
>>>>>
>>>>
>>>> ok, but wouldn't it be better to introduce an option like
>>>> CONFIG_SYS_NS16550_UME instead of using the SoC-specific
>>>> CONFIG_ARCH_JZ47XX. This driver is messed up enough ;)
>>>
>>> I was undecided between this (like the IER) and adding new ifdef (like
>>> SOC_KEYSTONE). Whichever way is fine with me. Yeah, the driver is
>>> repugnant for sure.
>>>
>>>>>>> +
>>>>>>>  #ifndef CONFIG_SYS_NS16550_IER
>>>>>>>  #define CONFIG_SYS_NS16550_IER  0x00
>>>>>>>  #endif /* CONFIG_SYS_NS16550_IER */
>>>>>>>
>>
>> That way seems better to me. You should be able to add your UME flag
>> as a Kconfig for this driver, in drivers/serial/Kconfig, which
>> defaults to 0. It would be good to keep out board-specific stuff from
>> this file, as you did with OMAP1510.
>
> I'm not really sure I want to expose the CONFIG_SYS_NS16550_FCR override
> via Kconfig. The extra bits should be set via DT props
> unless there is some really good reason why that cannot be done
> (like size limitation in SPL or DT not available).
>
> I tried these approaches:
> 1) Add Kconfig option for CONFIG_SYS_NS16550_FCR , where you
>    set specific byte value. This makes it hard to figure out
>    which bits are set in the FCR just by looking at the value.
> 2) Add Kconfig option selected if ARCH_JZ47XX is selected and
>    use that in the driver to add the extra UME bit.
> 3) Define CONFIG_SYS_NS16550_FCR in include/configs/board.h
>    using the macros from ns16550.h . This makes it obvious
>    which bits are set.
>
> I am undecided between 2 and 3, but inclined to go with 3.
> What do you think ?

How about making your feature an option, like CONFIG_SYS_NS16550_UEN,
which defaults to 0, but in your case is 0x10. You can OR it into the
value.

Regards,
Simon